The invention relates to Hepatitis C virus-epitopes, which are specific with respect to CD4+ T-lymphocytes, and to vaccines containing these epitopes.
The Hepatitis C virus, termed HCV in the following, was identified in 1989 and is an RNA virus from the family of flaviviridae. It consists of one single strand of RNA of approx. 9400 nucleotides which code a precursor polyprotein of about 3000 amino acids in length. This polyprotein is translated in an open reading frame and split post-translationally and proteolytically. The virus is highly variable and various virus isolates exist which are designated as genotypes and the geographical distribution of which varies largely. More than six genotypes throughout the world have now been differentiated. These genotypes are in turn subdivided into subtypes. The genetic variability is present inter-individually and intra-individually (within an infected individual). The intra-individual subtypes are the so-called HCV quasi-species which are related but different virus sequences occurring with imprecise replication.
With a prevalence of approx. one to three percent world-wide, Hepatitis C is one of the most important chronic virus infections. At least 180 million individuals are thought to be currently infected. According to calculations by the Center of Disease Control in the USA, due to the long latency period after infection with HCV, there will still be an increase in illness associated with Hepatitis C until the year 2010.
The HCV is primarily transmitted parenterally and, until it was discovered, it was the main cause of post-transfusion hepatitis NonA-NonB. Due to the testing of all blood products on a routine basis with HCV antibody tests of the 2nd and 3rd generation, the number of post-transfusion hepatitis cases has reduced drastically. The so-called sporadic Hepatitis C infections. Currently there are no known measures of effectively preventing new infections along these routes.
The HCV causes a chronic inflammation of the liver (hepatitis) which in the course of many years can lead to other complications such as liver cirrhosis. Within the framework of a liver cirrhosis lasting some years about 5% of all infected persons develop a hepatocellular carcinoma. Consequently, in the western world Hepatitis C takes the first place as the cause of liver transplantations. The costs for the public health service due to these transplantations are substantial.
Although with chronic Hepatitis C antibodies can be found against almost all virus proteins, in contrast to Hepatitis B however, there is no anti-HCV antibody constellation which indicates an immunity to HCV or a cure. Also the presence of antibodies against the HCV during a chronic HCV infection does not alleviate the course of the illness. On the contrary, a successful therapy appears to be linked to a reduction in the antibody titre. Therefore, it is not possible to prevent an infection with Hepatitis C through a conventional, prophylactic vaccination with envelope protein as is successfully carried out with Hepatitis B. A therapeutic vaccination is therefore currently not available.
The only currently approved therapy is a treatment with interferon-alpha alone or in combination with ribavirin for three to twelve months. This form of therapy is very cost-intensive, it often involves side effects and leads to a permanent elimination of the virus in only about 40% of cases.
From the Journal of Virology, Volume 71, pages 6011 to 6019 and Hepatology, Volume 30, No. 4, 1999, pages 1088 to 1098 it is known that through direct peripheral blood T-cell stimulation and specificity analysis of HCV-specific T-cell lines, highly immunogenous T-cell epitopes can be identified within the core and NS3 and NS4 regions of the Hepatitis C virus. Here, T-lymphocytes are isolated from peripheral blood and the CD4+ T-lymphocytes specific to HCV which it contains are enriched to so-called specific T-cell lines by repeated stimulation with the appropriate virus protein in vitro. Through the analysis of the growth behaviour (inclusion of radioactively labelled nucleotides) of these specific T-cell lines after stimulation with HCV protein and/or the smaller subunits, the peptides, the sequence of the T-cell epitope can be narrowed down. In particular the analysis of T-cell lines produces in comparison to T-cell clones inexact results with regard to the sequence specifically recognised by the CD4+ T-lymphocytes due to the cell mixture.
It is therefore the object of this invention to isolate HCV epitopes specific to CD4+ T-lymphocytes and to make available the HCV epitopes identified through the CD4+ T-lymphocytes for a vaccine for the prophylaxis and/or therapy of an HCV infection.